Question 1

Consider the following code snippet:
Public static <E> void print(E [] a) {
For (int i = 0; i < a.length; i++)
{
System.out.println(a[i] + " ");
}
}
Int[] a = {3,6,5,7,8,9,2,3};
String[] s = {"happy","cat","silly","dog"};
Boolean[] b = {true, true, false};
Which of the following are correct calls to this generic print method?
I print(a);
II print(s);
III print(b);

Accepted Answer

The answer of Consider the following code snippet:
Public static <E>...

Question 2

Which of these Java library classes are implemented using type variables?
I HashMap
II LinkedList
III ArrayList

Accepted Answer

All three classes (HashMap, LinkedList, and ArrayList) are implemented using type variables. HashMap uses type variables for the key and value types, while LinkedList and ArrayList use type variables for the element type. Type variables provide flexibility and type safety by allowing a class to work with different types of objects without knowing the exact type at compile time.

Question 3

Select the correct header for this generic print method.
Public static void print(E[] a) {
For (int i = 0; i < a.length; i++)
{
System.out.println(a[i] + " ");
}
}

Accepted Answer

The method is a generic method with a type parameter E. The type parameter is used to specify the type of the elements in the array that is being printed. The method is also declared as public and static, which means it can be accessed from other classes without creating an instance of the class.

Question 4

The type variables in HashMap<K, V> in the standard library mnemonically represent ____.

Accepted Answer

The type variables K and V in HashMap represent key and value respectively. This is because a HashMap is a data structure that stores a mapping between keys and values.

Question 5

Consider our own generic class MyLinkedList shown below. It has a private Node class, and it implements the standard Java ListIterator generic interface. Public class MyLinkedList { Private MyNode first; ) . . Private class MyNode { Private E data; Private MyNode next; } Private class MyIterator implements ListIterator { ) . . } } Which of the following statements apply? I the code is correct II change to private class MyIterator implements ListIterator III change to private class MyNode

Accepted Answer

The code is correct. The MyNode class is private to the MyLinkedList class, and the MyIterator class implements the ListIterator interface.

Question 6

Determine the correctness of the MyLinkedList generic class code below.
Public class MyLinkedList<E>
{
Private MyNode first;
Public E getFirst() { return first.data; }
Private class MyNode
{
Private E data;
Private MyNode next;
}
}

Accepted Answer

The code is correct. The inner class MyNode can be private, and MyNode can refer to the type variable E. The first.data will not cause a compiler error because first is of type MyNode, which has a data field of type E.

Question 7

Which argument type cannot passed to generic methods?
I Object
II GUI components
III primitive

Accepted Answer

The answer of Which argument type cannot passed to generic...

Question 8

Which of the following statements about generic methods is correct?

Accepted Answer

A generic method must have at least one type parameter declared with the angle bracket notation before the method's return type. This allows the method to work with multiple types. A generic method doesn't have to reside in a generic class and doesn't have to have a generic type argument. The generic type parameter of a generic method designates the type parameter for the method, not the return type.

Question 9

Determine the output of the MyLinkedList generic class code below when the main method executes.
Public class MyLinkedList<E>
{
Private MyNode first;
Public MyLinkedList(E

Accepted Answer

When the main method executes, it creates a new MyLinkedList object called "list" with a first element of "Hello". The method then calls the getFirst() method, which returns the value of the first element (in this case, "Hello"). The output of the program is "List first element = Hello".

Question 10

Consider the following code snippet:
Public static <E> void print(E[] a)
{
For (int i = 0; i < a.length; i++)
{
System.out.println(a[i] + " ");
}
}
Int[] a = {3,6,5,7,8,9,2,3};
Print(makeArray(a));
Assume that the method call to print(makeArray(a)) works correctly by printing the int array a. Which of the following headers for the makeArray method will make this possible?
I public static Integer[] makeArray(int[] a) 
II public static E[] makeArray(int[] a) 
III public static Integer[] makeArray(E[] a)

Accepted Answer

The print method is expecting an array of type E, which is a generic type. In this case, the array being passed in is of type int[].

Therefore, in order for makeArray to work correctly, it needs to return an array of type E, which should be Integer in this case as int cannot be cast to E.

Choice I is correct because it returns an array of Integer[], which matches the type expected by the print method.

Choice II is incorrect because it returns an array of type E[], which is not specific enough to match the expected type of the print method.

Choice III is incorrect because it takes an array of type E[], which is not the correct type for the input array.

Question 11

In Java, generic programming can be achieved with ____.

Accepted Answer

The answer of In Java, generic programming can be achieved...

Question 12

Consider the following code snippet: Public class Box { Private E data; Public Box(){ . . . } Public void insert(E value) { . . . } Public E getData(){ . . . } } What specific exception will be thrown when the following code executes? Box box = new Box(); ) . . Box)insert("blue Box"); Double myDouble = (Double) box.getData();

Accepted Answer

The code will throw a ClassCastException because we are trying to cast a String object to a Double object. This is not possible and will result in a ClassCastException.

Question 13

Which of the following statements regarding restrictions for generic methods are true?
I Generic methods must be declared inside a generic class.
II Generic methods must be static.
III Generic methods may only have one generic parameter.

Accepted Answer

The answer of Which of the following statements regarding restrictions...

Question 14

What is the best technique for overcoming the restriction for the use of primitives, such as int, in generic classes and methods?

Accepted Answer

The best technique for overcoming the restriction for the use of primitives in generic classes and methods is to use wrapper classes. Wrapper classes such as Integer, Double, Boolean, etc., can be used in place of primitive types, and they provide additional functionality such as conversion to and from a String, comparison methods, and more. This allows generic classes and methods to work with primitive values as if they were objects. Using Object types (A) or String with decode values (C) can lead to runtime errors and decreased performance, while not using generic methods with primitives (D) may limit the reusability and flexibility of the code.

Question 15

Which of the following headers for a generic method myMethod allows the actionPerformed method from the ActionListener class to be called? I public static E myMethod(E e) II public static E myMethod(E e) III public E myMethod(E e)

Accepted Answer

The correct syntax for a generic method that ensures the parameter type extends a specific class or interface is "extends". Therefore, both I and III are correct as they use "extends ActionListener". "Implements" is not valid in this context for generic type bounds.

Question 16

An inner helper class, such as a TreeNode inside the generic BinaryTree class, must meet which of the following criteria?
I be public
II be private
III be declared as generic

Accepted Answer

The answer of An inner helper class, such as a...

Question 17

Consider the following declaration: LinkedList list = new LinkedList(); This declaration implies that the LinkedList class could begin with which of the following code statements? I public class LinkedList { . . . } II public class LinkedList ~~{ . . . } III public class LinkedList { . . . }~~

Accepted Answer

The answer of Consider the following declaration:
LinkedList<String> list = new...

Question 18

What is known for certain about a type parameter when a method constrains it as follows?
<E extends MouseListener & MouseMotionListener>

Accepted Answer

The answer of What is known for certain about a...

Question 19

What is known for certain about Visualizer when a method constrains its type parameter as follows?
<E extends Visualizer>

Accepted Answer

The constraint <E extends Visualizer> allows E to refer to either a class or an interface that implements the Visualizer interface. Therefore, Visualizer can refer to either an interface or a class.

Question 20

Which of the following statements about generic methods is correct?

Accepted Answer

The answer of Which of the following statements about generic...

Quiz 18: Generic Classes

Which of these Java library classes are implemented using type variables? I HashMap II LinkedList III ArrayList

Select the correct header for this generic print method. Public static void print(E[] a) { For (int i = 0; i < a.length; i++) { System.out.println(a[i] + " ") ; } }

The type variables in HashMap<K, V> in the standard library mnemonically represent ____.

Determine the correctness of the MyLinkedList generic class code below. Public class MyLinkedList<E> { Private MyNode first; Public E getFirst() { return first.data; } Private class MyNode { Private E data; Private MyNode next; } }

Which argument type cannot passed to generic methods? I Object II GUI components III primitive

Which of the following statements about generic methods is correct?

Determine the output of the MyLinkedList generic class code below when the main method executes. Public class MyLinkedList<E> { Private MyNode first; Public MyLinkedList(E

In Java, generic programming can be achieved with ____.

Which of the following statements regarding restrictions for generic methods are true? I Generic methods must be declared inside a generic class. II Generic methods must be static. III Generic methods may only have one generic parameter.

What is the best technique for overcoming the restriction for the use of primitives, such as int, in generic classes and methods?

An inner helper class, such as a TreeNode inside the generic BinaryTree class, must meet which of the following criteria? I be public II be private III be declared as generic

What is known for certain about a type parameter when a method constrains it as follows? <E extends MouseListener & MouseMotionListener>

What is known for certain about Visualizer when a method constrains its type parameter as follows? <E extends Visualizer>

Which of the following statements about generic methods is correct?